It is known in the art to provide efficient power supply generation circuitry for, in particular, power amplifier applications. Power amplifiers, for example radio frequency (RF) power amplifiers, typically have high peak-to-average (PAR) ratios. If a power supply voltage is provided which is sufficient to deal with the voltage peaks, then for a large portion of the operation of the amplifier the power supply voltages are unnecessarily high, and the operation of the power amplifier is highly inefficient.
For this reason, efficient power supply generation means have been developed. Typical techniques fall into the broad categories of envelope elimination and restoration (EER) and envelope tracking (ET).
An efficient envelope tracking voltages supply scheme is described in UK Patent No. 2398648 in the name of Nujira Limited.
Prior art efficient envelope tracking power supplies operate efficiently for narrowband signals. However for wideband signals, inefficiencies arise. This is due to excessive switching losses and distortion as a result of having to adapt the power supply to handle a wide range of frequencies.
It is an aim of the invention to provide an improved technique for efficiently providing a power supply voltage, preferably over an increased bandwidth.